The dopaminergic tuberoinfudibular neurons (TIDA) are generally believed to have an important role in the regulation of the secretion of the anterior pituitary, particularly in relation to prolactin release. On the other hand, the hormonal and the hypothalamic neurotransmitter inputs to the TIDA neurons and the influence that these inputs have on the activity of the TIDA neurons have not been extensively investigated. Identification of some of the hormonal and neurotransmitter input to TIDA neurons will provide significant insight into the next higher level of the hypothalamic control of anterior pituitary function. The objectives of the experiments outlined in this proposal are to investigate possible noradrenaline (NA) serotonin (5-HT), LHRH or LH input onto TIDA neurons. In separate studies each of the above agents will be infused into the 3rd ventricles of female Sprague-Dawley rats via a permanently implanted guide tube. The effects of this treatment on the content and turnover of DA in the arcuate nuclei, median eminence and intermediate lobe-neurohypophysis complex will be determined with the use of extremely sensitive analytical methods for DA quantitation. These specific hypothalamic and pituitary regions represent the sites of origin and termination, respectively, of TIDA neurons. Subsequent experiments will determine if effects of these agents are directly on TIDA neurons, whether these effects are mediated within the medial basal hypothalamus and whether the effects are influenced by gonadal steroids.